Kara was the only daughter of Zor-L, a Kryptonian expert in sciences of the mind. Heeding his brother Jor-L's prediction
of the impending destruction of Krypton, Zor-L hastily constructed
a spaceship to carry his daughter to Earth.

While Jor-L's son, Kal-L (Superman) was rocketed directly to Earth, Kara's ship
to a less direct route. Conserving fuel and concentration on the mental development of Kara the so-called symbioship kept her
alive in suspended animation and crafted an artificial reality educating her in the ways of Krypton.

Arriving on Earth, Kara's ship was discovered by a now adult Superman, who helped his cousin adjust to human society.
Shortly thereafter she joined the Justice Society of America as
Power Girl.